Insulin and other injectable medications are commonly administered with drug delivery pens, whereby a disposable pen needle assembly is attached to facilitate drug container access and allow fluid egress from the container through a needle into the patient.
The assembly and operation of a typical drug delivery pen are described in U.S. Patent Application Publication No. 2006/0229562 to Marsh et al., published on Oct. 12, 2006, which is hereby incorporated by reference in its entirety. Drug delivery pens typically include a dial function that can control the exact amount of dosage that is injected. However, the exactness of the dosage is based on the assumption that the main components of the drug delivery pen, namely a main body with a dosage dialing function and a medicament cartridge holder holding a liquid medicament cartridge, are connected together properly. A drive mechanism, such as a piston, extends from the main body against the medicament cartridge housed in the cartridge holder, and its movement is based on proper attachment of the main body to the cartridge holder. However, a proper connection between the main body and the cartridge holder may be lost due to user error or some form of vibration or unintended force that causes an unwanted partial separation between the main body and the cartridge holder.
Accordingly, a need exists for an improved drug delivery pen that can alert a user that key components thereof are not properly connected, which would result in an improper dosage of medicament being delivered to a user.